1. Field of the Invention
This invention relates to an apparatus and a method. More specifically, this invention is directed to an electrostatographic apparatus equipped with an improved fluidized bed reactor for reduction of ozone emissions into the ambient environment.
2. Description of the Prior Art
The adverse effects of ozone on equipment and human beings is well-known. With the enactment of OSHA and the subsequent setting of tolerance levels pursuant to this legislation, the industrial community has intensified its efforts to minimize generation of ozone in its processes and equipment. The need for control of ozone emissions from equipment is especially critical in the area of consumer products since the user of such devices is ordinarily unaware of the hazard and unlikely to take precautions to protect himself.
As is well known, ozone is generated in electrostatographic copying equipment as a result of corona discharge during sensitization of the recording surface of the photosensitive member. This is also true of other stations within the copier which employ corona discharge devices. At present, ozone emissions into the surrounding machine environment are controlled by "filtering" devices which are impregnated with catalysts capable of conversion of the ozone to relatively harmless substances. Of course, the efficiency of catalytic neutralization of ozone is dependent upon a number of factors. At present, the ozone "filtering" devices employed in electrostatographic copiers are located in the copier exhaust stream. These filters are generally characterized as "fixed" bed devices; that is, the catalyst is impregnated into a porous support which is integrated within the copier exhaust housing (IBM Technical Disclosure Bulletin, Vol. 11:8, January 1969); or is incorporated into the corona discharge electrode structure itself (U.S. Pat. No. 3,675,096). Each type of ozone control system described hereinabove is limited in its ability to neutralize the ozone due to the physical constraints placed upon the catalysts containing element.
As will be appreciated, the amount of exposure of the ozone laden vapors to catalyst determines the capacity and efficiency of ozone neutralization by the catalyst containing element. Where the catalyst is entrained within or coated upon a porous or fibrous support, ozone laden vapors must be capable of penetration of this structure for contact with the catalyst. At first, it would appear that this would not present any problems. However, it must be remembered that ozone laden exhaust produced by electrostatic copiers also contains numerous particulates (e.g. toner, paper fragments, etc.). These particulates can pass with the ozone laden exhaust to the catalyst support and, after a relatively brief period, impregnate the support material thereby diminishing the porosity of the catalyst containing element. As the porosity of the support decreases, so to does the amount of catalyst accessible to the ozone laden vapors. The above situation can require frequent replacement of the catalyst containing element or some sacrifice in the completeness of exhaust treatment in order to extend catalytic activity of the "filtering" device.
In order to eliminate many of the deficiencies in the prior art devices, a co-worker of mine has proposed replacement of the traditional type of fixed bed ozone neutralization filters with a fluidized bed reactor system (copending patent application filed by William K. Murphy on or about June 29, 1977 -- U.S. Ser. No. 812,195 -- Xerox docket file designation D/77221). As acknowledged by Murphy at page 8, line 19 to page 9, line 8 of his specification, fluidization of the catalytically active materials within his reactor results in the generation of very fine particles of catalyst and carrier. In order to prevent such particles from being expelled into the copier environment Murphy suggests entrapping such materials within the perforated disc which is located proximate to the exhaust end of the reactor, or by providing for precipitation of such particles upon their escape from the reactor. With regard to his latter suggestion, such precipitation involves introduction of yet another station within the copier and disposal of the collected materials. In the event that fine particulates become entrapped within the perforated disc proximate to the exhaust port, the pressure differential between the interior of catalyst containing chamber and the exterior of said chamber proximate to the exhaust end of the chamber will increase as restriction to flow through the perforated disc becomes more pronounced. As is well known, if this differential or pressure drop becomes too great, fluidization of the catalysts will become impaired. In order to avoid a reduction in the efficiency of Murphy's device, the perforated disc proximate to the exhaust end of the reactor must be periodically serviced (back flushed) or replaced. This would require additional hardware or increased servicing costs.
Accordingly, it is the object of this invention to remedy the above as well as related deficiencies in the prior art.
More specifically, it is the principal object of this invention to provide a catalyst containing element for neutralization of ozone laden vapor which is less subject to fouling by particulates than prior art devices and yet does not allow for substantial by-pass of the ozone laden vapors.
It is another object of this invention to provide a catalyst containing element for neutralization of ozone laden vapors which has extended catalytic activity.
It is yet another object of this invention to provide a catalyst containing element for neutralization of ozone laden vapors in an electrostatographic copying system.
Still yet additional objects of this invention include a method for control of ozone emission levels of electrostatographic copiers and electrostatographic copiers which include an improved ozone neutralization catalytic element.